Process of separating wax from mineral-oil lubricating stock



Aug. 14, 1923. 1,464,707

C. H. HAPGOOD PROCESS 0F SEPARATING WAX FROM MINERAL OIL LUBRICATING STOCK Filed Oct. 22, 1921 2 Sheets-Sheet 1 HMM olv/H Aug.

C. H. HAPGOOD PROCESS OF SEPARATING WAX FROM MINERAL OIL LUBRICATING STOCK wH-rfrr i Wrth' Filed Oct. 22

2 Sheets-Shea @ffm/ F/GZ.

@ras Alda-)ard //ayvyooa/ Patented Aug. 14, 1923.I

UNITED STATES PATENT OFFICE.

CYBUS HOWARD HAPGOOD, 0F NUTLEY, NEW JERSEY, ASSIGNOR T0 THE DE LAVAL REPARATUR COMPANY, 0F NEW YORK,

N. Y., A CORPORATION 0F NEW JERSEY.

PROCESS OF SEPARATING WAX FROM MINERAL-OIL LUBRICATING STOCK.

Application med october 22, 1921. Vserial nu. 509,699.

To all whom it may concern:

Be it known that I, CYRUs HowARD HAP- Goon, a citizen of the United States, residing at Nutley, county of Essex, and State of New Jersey, have invented a new and useful Improvement in Processes of Separating Wax from Mineral-Oil Lubricating Stock, of which the following is a full, clear, and exact description, reference beingr had to the accompanying drawings, which form a part of this Specification.

In the refining of parailin base crude oil, it is customary to distill ofi` successively products of successively higher boiling points, such as naphtha, illuminating oil, gas oil and wax distillates, leaving as a residue what is commonly known as cylinder stock or bright stock. This bright stock carries in solution a substantial proportion of amorphous wax (petrolatum) which it is necessary or desirable to separate from the oil. The wax distillates carry in solution a substantial proportion of crystalline wax (paraffin) which it is necessary or desirable to separate from the oil.

It is known to effect the separation of wax from bright stock by diluting the stock with naphtha, bringing the blended stock in heat exchange relation with refrigerated brine for the purpose of throwing the wax out of solution, then separating the wax from the oil by filtration or settlement, and distilling off the naphtha.

It is also known to effect the separation of Wax from wax distillates by similarly cooling with refrigerated brine followed by ltration or settlement.

The settlement and filtration processes are bulk processes, involving the use of large plants occupying much room, the handling of a large amount of stock at one time and the expenditure of considerable time. An expensive part of the plant is that required to provide refrigerated brine in quantity suiiicient to cool and maintain cold the bright stock or wax distillate; while the cold carried by the oil after the separation therefrom of the wax is largely or wholly wasted. The refrigerating part of the plant is therefore both e nsive and uneconomic.

The object of this invention is to carry on the proces continuously instead of in batch, to substitute a small, eilicient and economical plant for a large, ineicient and wasteful plant, and particularly to simplify and cheapen the refrigeratin treatment. In eii'ecting this result I avai myself of known expedients, such as heat (or .cold) exchange, chilling by direct absorption of heat by ammonia, and centrifugation, all combined to form a process which is unitarily new.

I am aware that it has been proposed to separate wax from cylinder stock continuously by refrigerating the stock and separating the oil and the precipitated waxes by means of centrifugal force, using brine as an agent to carry the wax out of the centrifugal bowl. This process is effective to separate the oil from the wax, but the resultant mixture of brine and wax is difficult of separation. My process does not necessarily involve, but preferably excludes, the use of cold brine to carry the wax out of the centrifugal bowl. In any case, neither of the centrifugal processes herein described are herein claimed per se, but only as a ste in combination with the preceding refrigerating treatments and other associated steps.

My treatment of bright stock and my treatment of wax distillates have certain features in common and these features, when associated as herein described, comprise my invention in its broader aspect. In view, however, of the difference between the two treatments` I shall describe each separately.

While my process is not limited to the employment of any particular apparatus, I prefer to use those illustrated somewhat diagrammatically in the drawings, in which- Fig. 1 is a diagram of an apparatus arran d to carry out my process as adapted to thi separation of amorphous wax (petrolatum) from bright stock.

Fig. 2 is a diagram of an apparatus arranged to carry out my process as adapted to the separation of crystalline wax (paraiiin) from wax distillates.

Referring first to Fig. 1: a is a tank containing bright stock with wax in solution and diluted with naphtha. This tank is connected with a double'pipe preliminary chiller comprising a pipe b adapted to convey the blended stock toward the final chiller or chillers, and a pipe c (in heat exchange relation with pipe b) adapted to convey the separated cold wax-free oil toward a still for driving oif the naphtha. The blended 'heat While the oil is Stock and the wax-free oil flow in opposite directions so that the stock graduallyloses radually heated to normal temperature. t may be assumed, for purposes of illustration, that the temperature of the stock is reduced in this chiller from (say) 90o F. to 45 F.

The preliminarily chilled blended stock then flows through an intermediate double pipe Chiller comprising a pipe d adapted to convey the stock to the final chiller and a pipe e (in heat exchange relation with pipe d) adapted to circulate ammonia which has been compressed, condensed and expanded in the manner well known in the art and known as the direct expansion system of refrigeration. The current of expanded, gaseous, low-temperature ammonia flows in a direction opposite to that of the stock and gradually reduces the temperature thereof until, when the blended stock emerges from the pipe d, it has been .substantially reduced in temperature, say to about 20o F.

The thus chilled blended stock then flows througha final double pipe chiller comprising a pipe d adapted to convey the stock to a centrifugal separator and a pipe e (in heat exchange relation with pipe d) adapted to circulate ammonia which has been compressed, condensed and expanded. The current of ammonia flows in a direction opposite to that of the stock and gradually reduces the temperature thereof until when the blended stock emerges from the {inal cooler it has been reduced to a temperature suliicient to throw all the wax out of solution. This final temperature may vary from -10. to 10 F. A. preferred temperature is somewhat below zero F.

In the separator f (which may be of the type shown in the Snyder Patent No. 1,283,- 343, dated October 29, 1918), the oil and wax are separated and separately discharged, the wax being pumped' through the pipe g to a still for separating and recovering the naphtha and the oil being pumped through the pi e L and through pipe c of the double pipe c iller, to a still in which the naphtha is driven oil'.

In the ammonia circulating system, 1I is the condenser, wherein the compressed ammonia at a high pressure is reduced in temperature. j is the ammonia reservoir. The ammonia pipes e and e of the last two chillers are arranged in parallel. The two pipes have independent expansion valves 1c and k', the ammonia, as it escapes through either valve, being greatly reduced in pressure and expanding from a liquid of relatively high temperature to a gas of very low temperature, as well known in the art. From the pipes e and e' the ammonia gas, which has absorbed heat from the stock, flows to the respective compressors a, z', wherein the ammonia is compressed and greatly elevated in tem erature, preparatory to condensation in con enser z', as before described.

It will be noted that the execution of the above process involves the use of a small and inexpensive plant; that while a small amount of stock is handled at one time, the process is continuous and that a large volume of stock may be treated in a. comparatively short time; and that the utmost economy in cost of operation is achieved. With respect to the last named advantage, it is clear that the lowering of the temperature of the incoming blended stock by heat absorption by the outgoing centrifugally separated oil is effected by means of a liquid that has been already necessarily rrefrigerated; that the expense of refrigeration is only that required to reduce the temperature of the stock through a comparatively small temperature range; and that the later chilling is effected by direct expension of ammonia and not by means of an ammoniarefrigerated intermediate 1i uid.

Referring to Fig. 2, which is an apparatus for the treatment of wax distillates: m is a. tank containing a wax distillate. This distillate need not be, and referably is not, diluted with naphtha. T e tank m is connected with a double pipe preliminary chiller comprising a pipe adapted to carry the distillate toward the final chiller, and a pipe o (in heat exchange relation'with pipe n) through which the separated cold waxfree oil travels on its 'way to storage.

The preliminarily chilled stock then flows through one or more double pipe chillers p, r forming part of a direct expansion ammonia refrigerating system the same as that diagrammed in Fig. 1. The distillate emerges from the final cooler reduced to a temperature of from 20 F. to 35 F., preferably about 25 F. At this temperature the crystalline waxes have been thrown out of solution.

It is more dicult to centrifugally separate from oil and discharge from the bowl crystalline wax than itis to separate and discharge amorphous wax. If no heavy liquid agent is added to sludge the Wax out of the bowl, no wax at all will be discharged y from the bowl unless, in the first instance, the distillate has been diluted with naphtha. Even the use of a sludging liquid, such as refrigerated brine, will not prevent the wax from building up rapidly within the bowl, and moreover the mixture of brine and wax is very diicult of separation. In the present process, I admit water, at a temperature of about 180 F, from a reservoir t, into the peripheral part of the separator bowl u, heat-insulating the water feed channel withinthe bowl from the distillate feed channel and from the separating compartment. The hot water flowing along the periphery of the bowl melts the la er of wax immediately adjacent thereto, and such wax, being in a liquid condition, readily flows out of the bowl. This part of the p-rocess is not herein claimed per se, as it is the joint invention of Selden H. Hall and myself and forms the subject-matter of an application filed September 8, 1921, Serial No. 499,325.

The separated cold wax-free oil from the centrifugal separator u is then pumped through the pipe o of the double plpe preliminary chiller and thence to storage. The melted wax and hot water discharge into a separator rv constructed on the principle of a Florence flash, in which the water (which is heavier than the wax) is continuously `syphoned off and thence pumped back to the tank t, while the waxes float oif the top and are either pumped direct to the sweating pans or may be freed from any water which they carry ofi' by treatment in a second centrifugal separator y.

The water in tank t is kept at the desired temperature by means of steam coils lw. The pipes in the coolers through which the distillate flows to the centrifuge are prevented from clogging with Wax by means of internal agitators on shafts to which are secured driven sprockets a'.

It will be evident that the just described process for treating wax distillates and the previously' described process for treating bright stock have features both of identity and similarity, and that to the extent that the processes are alike, the advantages are the same.

While that step of the refrigerating treatment comprising the cooling of the stock by direct expansion of ammonia may be carried out in a single chiller instead of in a plurality of chillers, as illustrated and described, I have found that the power required (measured in terms of H. P. hours to make one ton of refrigeration) will diminish with the number of chillers emiployed. The use of at least a plurality of chillers is therefore not a mere matter of convenience, or a mere duplication, but effects a substantial saving in cost of refrigeration.

I have not herein claimed the apparatus for carrying out my procs, as the same forms the subject of an application for gt- ,ent filed by me October 11, 1922, Serial 0.

593 674, as a division hereof.

I-laving now fully described my invention, what I claim and desire to protect by Letters Patent is:

1. The process-of treating lubricating oils containing waxes in solution to separate the wax from the oil which comprises subjecting the stock to two successive refrgerating treatments, thereby throwing the waxes out of solution, and then subjecting the oil and precipitated wax to centrifugal force and separately discharging the oil-free wax and the wax-free oil; the rst refrigerating treatment comprising flowing the wax-free oil into heat exchange relation with the stock whereby the former absorbs heat from the latter, and the second refrigerating treatment comprising the cooling of the stock by direct expansion of ammonia.

2. The process of treating lubricating oils containing waxes in solution to separate the wax from the oil which comprises subjecting the stock to two successive refrigerating treatments, thereby throwing the waxes out of solution, and then subjecting the oil and precipitated wax to centrifugal `force and separately discharging the oil-free wax and the wax-free oil; the :rst refrigerating treatment comprising owing the wax-free oil into heat exchange relation with the stock whereb the former absorbs heat from the latter, an the second refrigerating treatment comprising a plurality of stages, in each of w ich the stock is cooled by direct expansion of ammonia, the pressure and temperature of the expanded ammonia being pro ressively lower in said successive s es o direct refrigeration.

n testimony of which invention, I have hereunto set my hand, at New York, on this 19th day of October, 1921.

CYRUS HOWARD HAPGOOD Witnesses:

Gao. D. TALLMAN, E. L. GARDNER. 

